The automaker says electric cars may be more polluting than vehicles with internal combustion engines if the electric power isn’t from a clean source. It estimates the level of carbon dioxide emitted by a gasoline-engine Mazda2 at about 9 percent less than the 162 grams-per-kilometer attributed to an electric version of the car whose power comes from a coal-fired plant.

“As long as conventional vehicles truly comply with regulations, electric cars won’t be needed to solve environmental issues,” Mitsuo Hitomi, a managing executive officer who heads Mazda’s technical research center, said in an interview in Tokyo Wednesday.

Hitomi’s comments contrast with plans by the world’s biggest automakers including Volkswagen AG, Ford Motor Co. and BMW AG to invest billions of dollars to electrify their lineups in the next decade. While Mazda is co-developing battery cars with Toyota Motor Corp., it has largely focused on refining performance through its Skyactiv fuel-efficient technology and intends to introduce the next-generation Skyactiv-X in 2019 with as much as 30 percent improvement in engine efficiency.

Fully replacing conventional cars with electric would require power output to double, Hitomi said, citing the carmaker’s own estimates. Costs would rise because the increase would be coming mainly from clean sources such as solar and wind, which are more expensive.

Electricity prices will also surge because drivers will typically be charging up at the same time of day, spiking peak demand, he said.

“Think about these negative consequences for consumers when you have more electric cars,” Hitomi said. “I personally don’t think the age for electric vehicles will ever come.”